The present invention relates to seals or packing which utilize a barrier or flush fluid. Particularly, the invention relates to a flush fluid control valve which incorporates a flow meter for accurate flush flow rate into a packed gland or a mechanical seal.
Clean flush injection is used to extend the life of mechanical seals or packing in many applications. Packed pumps or pumps with mechanical seals often have clean flush water injection through a lantern ring port on the pump casing. The flush water serves several purposes: to lubricate packings and seals on pumps that frequently break prime or run dry or where the working fluid has poor lubricating properties; to prevent premature packing or seal failure due to abrasive particles in the working fluid; and/or to ensure that leakage from the packing or seal to the external environment will be an innocuous liquid, e.g. water.
While continuous injection of clean flush water is required for long seal life, the actual flow rate needed is low. However, in the past, it has been difficult to maintain flow rates in the required ranges. Column flow gauges can be provided, and while inexpensive, quickly become occluded with pipe scale.
Additionally, maintenance personnel, aware of the need to flush seals, often resort to the use of excess flush water to avoid unscheduled downtime. Modern environmental laws and conservation efforts demand improved monitoring and control to minimize water consumption in these systems.